Prompt gamma imaging in proton therapy - status, challenges and developments

This paper is an overview of the field of proton therapy monitoring in real time using prompt gamma radiation. Different approaches providing either integrated or differential information are described, and their maturity, limitations and clinical usefulness are discussed. In the second part, the SiFi-CC project is briefly introduced, which aims at the development of a Compton camera for prompt gamma imaging, entirely based on fibres made of a heavy, inorganic scintillator read out by silicon photomultipliers. This compact solution offers very good timing properties, high granularity and a modern data acquisition system, addressing previously identified issues.